Plasma oscillations in a two-dimensional semimetal

Collective oscillations of an electron-hole plasma in a two-dimensional semimetal have been investigated. It has been shown that two undamped branches of plasma oscillations exist under certain conditions on the parameters of the structure. Acoustic plasmons are not damped in a finite wavenumber range. When the Fermi velocities of the electrons and holes are equal to each other, this range expands to the range of the applicability of the theory (the momentum of the plasmon is much lower than the Fermi momenta of the particles).